In known technique, for example when phase detecting in phase locked loops, the phase difference between two signals is usually measured by starting counting pulses of known frequency at the positive edge of the reference signal and stopping counting at the positive edge of the controlled signal, the phase difference between the signals being determined by the number of pulses.
The disadvantage of this solution is that in order to obtain sufficient measuring precision the pulses must be of a sufficiently high frequency that such an arrangement is difficult to realize in TTL-technique. Consequently this will imply a more complicated component choice resulting in higher costs.